Phase influence on the mechanical, electrical, and magnetic properties of Al0.8CoCrFeNi high-entropy alloy correlated with phase fractions determined by a new XRD quantification protocol

초록

We investigate phase evolution and multifunctional properties in Al<inf>0</inf>.<inf>8</inf>CoCrFeNi following homogenization at 1300 °C for 24 h and subsequent aging at 800, 900, and 1000 °C. A newly developed X-ray diffraction analysis protocol quantifies BCC_A2, BCC_B2, σ, and FCC_A1 despite database sparsity, and is cross-validated by EBSD and TEM. The homogenized matrix forms a bicontinuous A2+B2 duplex with dense A2/B2 interfaces and antiphase-domain walls, which maximizes electron and phonon scattering and therefore yields the highest resistivity, the lowest room-temperature thermal conductivity, and soft ferromagnetism governed by an B2 backbone with locally ordered A2 lamellae. Subsequent aging drives a transformation of A2 phase into A1 or σ that systematically tunes hardness, electrical/thermal conductivity, and magnetic response. At 800 °C, complete consumption of A2 and formation of a B2+σ+A1 multiphase aggregate increase hardness by ~ 30 %, while the reduced A2/B2 interfacial density and partial annihilation of antiphase-domain walls relax phonon scattering and raise both electrical and thermal conductivities. Aging at 900–1000 °C promotes A1 coarsening with minimal σ precipitation, lowering the density of coherent interfaces and leading to reduced electrical resistivity, convergence of thermal conductivities to intermediate values, and a drop in hardness, most markedly at 1000 °C where the A1 fraction and precipitate coarsening are highest. Magnetization in aged states at 800–1000 °C exhibits a significant loss of ferromagnetism due to the loss of local chemical order in A2. Collectively, these results show that the mechanical, electrical, thermal, and magnetic properties of this alloy are governed by aging-induced phase evolution. The study further demonstrates that the new X-ray diffraction protocol provides reliable secondary phase quantification in high-entropy and other complex alloys with limited crystallographic databases. © 2025 Elsevier B.V.

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